Electrical circuit breakers are utilized throughout electrical power transmission and distribution systems to interrupt the flow of electric current to a protected load. A conventional circuit breaker includes a pair of separable (main) contacts that open in response to a fault condition (e.g., overcurrent or ground fault) to interrupt the current flow. Auxiliary position switches are typically mounted to the frame of the circuit breaker to provide an electrical signal indicative of the position of the main contacts.
A typical auxiliary switch includes a separable contact structure in which one contact is disposed on a stationary contact arm, while the other contact is disposed on a movable contact arm. A spring generally urges the movable contact arm about a pivot to position the contacts in a normally open or normally closed state. A plunger engages the movable contact arm for opening the separable contacts in the normally closed configuration or for closing the separable contacts in the normally open configuration. When the plunger is depressed, it moves the movable contact arm to open or close the contacts accordingly.
Typically, the plunger of the auxiliary switch is actuated by a solid mechanical link to an operating mechanism in the circuit breaker, which acts to separate the main contacts of the circuit breaker. The plunger is displaced upon rotation or displacement of the movable contact arm. The displacement of the auxiliary switch plunger separates (or joins) the contacts in the auxiliary switch, which causes an electrical signal to be sent to a local or remote alarm, light or other monitoring device, thereby indicating the position of the separable contacts in the circuit breaker.
The force used to overcome the auxiliary switch spring and actuate the auxiliary switch is the same force used to separate the contacts in the circuit breaker. This force is typically provided by main springs in the operating mechanism of the circuit breaker. However, the use of the force provided by the main springs to actuate the auxiliary switch reduces the amount of force available to separate the contacts. Increasing the size of the main springs can compensate for the reduced force. However, increasing the size of the springs may not be desirable, since a corresponding increase in the size of the circuit breaker housing may result.
The above discussed and other drawbacks and deficiencies are overcome or alleviated by an auxiliary switch activation mechanism provided for use with a circuit breaker having an auxiliary switch and an operating mechanism for opening and closing main electrical contacts. In an exemplary embodiment of the present invention, the auxiliary switch activation mechanism includes a lever having a first end removably connectable to the operating mechanism, a second end of said lever removably connectable to the auxiliary switch, and a spring, mechanically coupled to the lever, which imparts a rotational bias on the lever. The lever provides an assisting force to the operating mechanism for opening the main electrical contacts.
In another embodiment, first end of the lever is removably connectable to a crank in the operating mechanism. The lever further comprises a foot which is slidingly engageable with a nose surface on the crank. The foot remains in contact with the nose surface when the circuit breaker main electrical contacts are in a closed position. Further, the foot is slidingly engageable with a bottom surface of the crank, and is removably engageable with the bottom surface when the circuit breaker main contacts are in an open or tripped position.
In yet another embodiment, the lever is substantially L-shaped and further includes a lip, which is removingly engageable with the auxiliary switch. The lever imparts a rotational force on the crank when the circuit breaker main electrical contacts are caused to be opened or tripped from a closed position.